For general information on trade associations, look in the Encyclopedia of Associations, which is available in print (in most business libraries), on Lexis (BUSREF;ENASSC) and on Dialog (File 114). Also check to see if the association has a Web site, and check the relevant news sources for articles.
Reports: The Investext Group sells reports published by trade associations. If you are looking for a specific report, it may be cheaper to contact the association directly (or an industry-specific library, if you know of one). For older reports, you can also search OCLC's WorldCat.